From the BLS website: The expenditure weight in the CPI for rent is obtained by directly asking sampled renter households the following question:
What is the rental charge to your CU for this unit including any extra charges for garage & parking facilities? Do not include direct payments by local, state or federal agencies. What period of time does this cover?
However, the expenditure weight in the CPI for rental equivalence is obtained by directly asking sampled owner households the following question:
If someone were to rent your home today, how much do you think it would rent for monthly, unfurnished and without utilities?
In English it means that, “rent of primary residence,” is just that rent paid by renters. “Owner equivalent rent,” is a more squishy figure derived from asking owners what their house would rent for.